Electric motor.



No. 676,520. Patnted :une la, |901.

A. yP. WARNER.

ELECTRIC MOTOR.

(Appl'iction me@ octh 22, 1900,)

(Ilo Model.)

ma nonmsys'rzns co. Now-LIM.. wAsnmron, n, a

` terminals B B2.

UNITED STATES PATENT OFFICE;

ARTHUR P. WARNER, OF MILWAUKEE, VISCONSIN, ASSIGNOR OF ONE- HALF TO THE NORTHERN ELECTRICAL MANUFACTURING COMPANY,

VOF MADISON, WISCONSIN.

ELECTRIC MOTOR.

SPECIFICATION formingpart of Letters Patent N o. 676,520, dated J' une 18, 1901.

Application filed October 22, 1900. Serial No. 33,850. (No model.)

To @ZZ whom, it tay concern.-

Be it known that I, ARTHUR P. WARNER, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State 'of Wisconsin, have invented a certain new and useful Improvement in Electric Motors,of which the following is a specification.

My invention relates to electric motors, and has for its object to provide a new and improved motor of this description.

In the accompanying drawing I have shown diagrammatically a motor embodyingmy invention.

This invention is particularly adapted for motors used under conditions necessitating frequent stopping and starting-s uch, for example, as motors for elevators, street-cars, and the like. Y

Referring now to the drawing, I-have illustrated diagram matically a shunt-motor A, provided with the ordinary shunt-windings B around the armature C, and a suitable starting-resistance D in the armature-circuit- The shunt B is connected to the main circuit in any desired manner-as, for example, at the The ordinary shunt-motor as now made is not adapted for use in connection with elevators and street-cars. By means of my invention, however, the objections to a shunt-wound motor when used under such conditions are obviated. In carrying out my invention I provide an additional held-winding E, which is wo und upon the ield-cores of the motor, this shunt being connectedacross the terminals D D2 of the rheostat or resistance D. This additional eldwinding is made of sufficient resistance to obtain the desired results. This resistanceqwill of course depend upon the conditions to be met. Ordinarily this additional field-winding will have a resistance greater than the starting-resistance, and in many instances this resistance will be live or six times the starting-resistance. v

When motors are used in connection with elevators and street-cars, theymust have a high starting torque, so that the armature can quickly attain sufcient speed -to develop the proper counter electromotive force, and then the field should be weakened, so as to permit a high speed. My invention permits this result to be obtained by the ordinary shunt-motor. the arm of the rheostat or starting-resistance is in the position shown in full lines in the drawing, thus interposing all of the resistance D in the armature-circuit. Under these conditions a .portion ofi the current iiows through the additional field-winding E, thusr reinforcing the ordinary shuntB. This results in a very strong field at the beginning, and hence a high starting torque is obtained. It will readily be seen that the effect of this additional field-winding can be controlled at will by varying its resistance. As the armature of the motor gains speed the starting-resistance D is cut out, and when normal speed is reached the entire resistance is preferably cut out, the arm being in the position shown in dotted lines in the drawing. As the starting-resistance is cut out itwill be seen that the current in the additional field-winding decreases and its effect upon the motor decreases, and when all the starting-resistance is cut out very little or no current will be passing through the additional field-winding, and hence it is rendered inoperative. It will thus be seen that by this means a high starting torque is obtained through the agency ofan additional field-winding, and then the additional field-winding is automatically, as it were, cut out when the motor has attained speed. I have found that this construction permits a shunt-motor to be used with highly satisfactory results in connection with elevators and street-cars.

In the drawing I have shown the additional -field-winding E as being shunted around all of the starting-resistance; but it is evident that this additional Jfield-.winding may be arranged in various manners, so as to be around onlya portion of this resistance.

rangements will of course readily occur to those versed in the art and will depend upon' the results desired and the conditions to be met.

When it is desired to start the motor,

Such ar- I clairny n l in the armature-circuit,whereby ahighstart- 1. An electric motor, comprising an arma-` ing torque is obtained, the additional fieldture, a shunt field- Winding around the arrna- AWinding being rendered'substantially inopture, a starting-resistance inthe armature erativewhen the' starting-resistance yis cut 5 circuit, and an additional Iield-Winding in out of circuit. l' v shunt around apart or all of the startinv-re- Y vv -f y .Sistance A i f v v D y ARTHUR P. WARNER. i i f 2. The combination with a shunt electric Witnesses: motor of an additional field-winding in shunt DONALD' M. CARTER.,

1o around a part or all of the starting-resistance HOMER L. KRAFT. 

